Incorporating differences between genetic diversity of trees and herbaceous plants in conservation strategies

Reviews that summarize the genetic diversity of plant species in relation to their life history and ecological traits show that forest trees have more genetic diversity at population and species levels than annuals or herbaceous perennials. In addition, among-population genetic differentiation is significantly lower in trees than in most herbaceous perennials and annuals. Possible reasons for these differences between trees and herbaceous perennials and annuals have not been discussed critically. Several traits, such as high rates of outcrossing, long-distance pollen and seed dispersal, large effective population sizes (N_e), arborescent stature, low population density, longevity, overlapping generations, and occurrence in late successional communities, may make trees less sensitive to genetic bottlenecks and more resistant to habitat fragmentation or climate change. We recommend that guidelines for genetic conservation strategies be designed differently for tree species versus other types of plant species. Because most tree species fit an LH scenario (low [L] genetic differentiation and high [H] genetic diversity), tree seeds could be sourced from a few populations distributed across the species’ range. For the in situ conservation of trees, translocation is a viable option to increase N_e. In contrast, rare herbaceous understory species are frequently HL (high differentiation and low diversity) species. Under the HL scenario, seeds should be taken from many populations with high genetic diversity. In situ conservation efforts for herbaceous plants should focus on protecting habitats because the typically small populations of these species are vulnerable to the loss of genetic diversity. The robust allozyme genetic diversity databases could be used to develop conservation strategies for species lacking genetic information. As a case study of reforestation with several tree species in denuded areas on the Korean Peninsula, we recommend the selection of local genotypes as suitable sources to prevent adverse effects and to insure the successful restoration in the long term.     

Levels of hexachlorobenzene and other organochlorine compounds in cord blood: exposure across placenta

Hexachlorobenzene (HCB) is an organochlorine compound widespread in the environment, highly lipophilic, that accumulates in biological systems. It has been suggested that it should be classified as a dioxin-like compound. Newborns are exposed to organochlorine compounds across the placenta and through breastfeeding. Although HCB is one of the most common organochlorine compounds, the transplacental transference of HCB from mother to fetus during pregnancy has been scarcely documented. This study reports the levels of HCB, dichlorodiphenyl trichloroethane (DDT) and its metabolite p,p'DDE, polychlorinated biphenyls (PCBs), and beta-hexachlorocyclohexane (beta-HCH) in 72 maternal blood samples at delivery and in 69 cord blood samples, from which 62 corresponded to mother infant pairs born between May 1997 and September 1999 in a rural area highly exposed to HCB. Results show that all newborns presented detectable levels of HCB, PCBs, and p,p'DDE, and, to a lesser extent, of beta-HCH, the HCB levels being the highest. The geometric mean of HCB was 1.1 ng/ml, ranging from 0.3 to 5.7 ng/ml. Concentrations of HCB levels in cord blood (log ng/ml) were positively associated with concentrations in maternal blood (log ng/ml) (coefficient = 0.45, P < 0.01). Gestational age was not associated with the transplacental transfer of HCB. Maternal p,p'DDE and beta-HCH levels were also associated with newborn levels, but levels of PCBs were not. We conclude that HCB, similar to other organochlorinated compounds, has a transplacental transfer.     

Microbial and physicochemical parameters associated with Legionella contamination in hot water recirculation systems

Hot water recirculation systems (HWRS) in hotels and nursing homes, which are common in countries such as Spain, have been related to outbreaks of legionellosis. To establish the relationships of microbial and physicochemical parameters, especially protozoa, with the occurrence of Legionella in HWRS, 231 samples from hotels and nursing homes were analysed for Legionella, protozoa, heterotrophic plate counts (HPC) at 22 and 37 °C, Pseudomonas, metals, temperature and others. Legionella pneumophila was the dominant species isolated, and 22 % were sg. 1. The sampling method became particularly important in order to define which factors were involved on the occurrence of Legionella. Results showed that the bacteria and the accompanying microbiota were more abundant in the first flush water whose temperature was lower. The bacteria occurred in those samples with high HPC and were inversely correlated with high temperatures. Multivariate regression showed that a concentration above 1?×?10⁵?CFU/100 mL of HPC at 37 °C, Fe above 0.095 ppm and the presence of protozoa increased significantly the risk of Legionella colonization, while univariant regression showed that the presence of Cu above 0.76 ppm and temperature above 55 °C diminished it. Therefore, to reduce the risk associated with Legionella occurrence in HWRS these parameters should be taken into consideration.     

Global fate of POPs: current and future research directions

For legacy and emerging persistent organic pollutants (POPs), surprisingly little is still known in quantitative terms about their global sources and emissions. Atmospheric transport has been identified as the key global dispersal mechanism for most legacy POPs. In contrast, transport by ocean currents may prove to be the main transport route for many polar, emerging POPs. This is linked to the POPs' intrinsic physico-chemical properties, as exemplified by the different fate of hexachlorocyclohexanes in the Arctic. Similarly, our current understanding of POPs' global transport and fate remains sketchy. The importance of organic carbon and global temperature differences have been accepted as key drivers of POPs' global distribution. However, future research will need to understand the various biogeochemical and geophysical cycles under anthropogenic pressures to be able to understand and predict the global fate of POPs accurately.     

In utero and post-natal accumulation of organochlorine compounds in children under different environmental conditions

A study of intake of organochlorine compounds (OCs) in children both in utero and at the age of four years has been performed in two cohorts. One encompasses children born in Menorca Island between 1997 and 1998, and the other those born between 1997-1999 in Ribera d'Ebre, an in-land industrial-agricultural area of Catalonia. Comparison of the OC concentrations in serum samples from both populations, including those obtained from cord blood and blood collected at four years, provides information on the influence of local pollution sources in the accumulation of these compounds. Statistically significant differences (p < 0.01) have been found for hexachlorobenzene, indicating that chronic airborne contamination to this compound in Ribera d'Ebre involved higher in utero exposure, which increased in the first four years of growth. Similarly, in the cohort of Menorca, higher in utero exposure to PCBs was observed and this increased subsequently in the first four years of growth. Other compounds encompassing temporal contamination episodes such as gamma-HCH involved higher in utero exposure but strongly diminished in the first four years of growth. Overall, it can be concluded that local chronic pollution by OCs has a direct effect in children living in the surrounding areas. This influence is reflected in higher exposure, both in utero and in the first years of growth, that significantly stands out over the background contamination due to the ubiquity of these compounds.     

Introduction of the Factor of Partitioning in the Lithogenic Enrichment Factors of Trace Element Bioaccumulation in Plant Tissues

Bioindicators are widely used in the study of trace elements inputs into the environment and great efforts have been conducted to separate atmospheric from soil borne inputs on biomass accumulation. Many monitoring studies of trace element pollution take into account the dust particles located in the plant surface plus the contents of the plant tissues. However, it is usually only the trace element content in the plant tissues that is relevant on plant health. Enrichment factor equations take into account the trace element enrichment of biomasses with respect soil or bedrocks by comparing the ratios of the trace element in question to a lithogenic element, usually Al. However, the enrichment equations currently in use are inadequate because they do not take into account the fact that Al (or whichever reference element) and the element in question may have different solubility-absorption-retention levels depending on the rock and soil types involved. This constrain will become critical when results from different sites are compared and so in this article we propose that the solubility factors of each element are taken into account in order to overcome this constrain. We analysed Sb, Co, Ni, Cr, Pb, Cd, Mn, V, Zn, Cu, As, Hg, and Al concentration in different zones of Catalonia (NE Spain) using the evergreen oak Quercus ilex and the moss Hypnum cupressiforme as target species. We compared the results obtained in rural and non industrial areas with those from the Barcelona Metropolitan Area. We observed differences in Al concentrations of soils and bedrocks at each different site, together with the differences in solubility between Al and the element in question, and a weak correlation between total soil content and water extract content through different sites for most trace elements. All these findings show the unsuitability of the current enrichment factors for calculating lithospheric and atmospheric contributions to trace element concentrations in biomass tissues. The trace element enrichment factors were calculated by subtracting the part predicted by substrate composition (deduced from water extracts from soils and bedrock) from total concentrations. Results showed that for most of the trace elements analysed, trace elements enrichment factors were higher inside the Barcelona Metropolitan Area than outside, a finding that indicates that greater atmospheric inputs occur in urban areas. The results show that the most useful and correct way of establishing a reference for lithospheric and atmospheric inputs into the plant tissues is, first, to analyse samples of the same plant species collected from a number of sites possessing similar environmental conditions (climate, vegetation type, soil type) and, second, to use this new enrichment factor obtained by subtracting from the total concentration in plant tissue the predicted contribution of soil or bedrock extracts instead of that of total soil or bedrock concentrations.     

Decontamination trends in the aquacultured fish gilthead seabream (Sparus aurata) after feeding long-term a PCDD/F spiked feed

Aquacultured fish gilthead seabream (Sparusaurata), previously exposed to low levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) trough the diet for a 13 months period, were fed on a clean feed for another 22 months. Gilthead seabream is a protandrous hermaphrodite species and this “decontamination” period coincided with the stages of sex differentiation, maturity and reproduction of the fish. PCDD/F levels in the fish tissues (i.e. muscle, liver, perivisceral fat and gonads), expressed in pg WHO-TEQ g⁻¹ fresh weight, showed a general decreasing trend during the “decontamination” period. However, this general trend varied among tissues and was also dependent on sex and lipid contents. Toxicological effects affecting fish behaviour and hepatic marker responses were also evaluated. The results pointed out that exposure to PCDD/Fs did not have an impact on fish development and reproduction, since the proportion of sexes found after the sex reversal process was within the normal range described for this species. In addition, long-term exposure to low PCDD/F levels did not significantly affect the response of most of the biochemical markers considered. On the contrary, some of them (e.g. EROD activity) showed variations in their responses during the sex differentiation process and onwards. Finally, the hepatic AhR mRNA levels increased during dioxin exposure but they returned to values typical for non-exposed fish after the “decontamination” period.     

Differential accumulation of mercury and other trace metals in the food web components of a reservoir impacted by a chlor-alkali plant (Flix, Ebro River, Spain): Implications for biomonitoring

Comparative studies of biomonitors of trace metal contamination are relatively scarce. We took advantage of a point source pollution in a reservoir (Flix, Spain) to compare trace metal (Hg, Pb, Cd, Se, As, Zn, Cu, Cr) bioaccumulation patterns among 16 food web components. Our results indicate that most organisms are suitable for Hg biomonitoring, whereas other metals are better monitored by only some of them. Biofilms and zebra mussel were the organisms with larger and more diverse biomonitoring capacity. However, we show that using groups of biomonitors increase the scope and strengths of the conclusions and specific goals can be better addressed. We conclude providing an overview of the strengths and weaknesses of the main organisms considered for biomonitoring trace metals in rivers and reservoirs.     

Altitudinal distributions of BDE-209 and other polybromodiphenyl ethers in high mountain lakes

The present study shows the occurrence of 2,2′,3,3′,4,4′,5,5′,6,6′-decabromodiphenyl ether (BDE-209) in microbial biofilms of Pyrenean and Tatra high mountain lakes despite its low vapor pressure and high hydrophobicity. Aerosol air transport is therefore a feasible mechanism for BDE-209 accumulation in sites up to 2688 m above sea level. This compound and other PBDEs exhibit altitudinally-dependent distribution involving higher concentrations with increasing mountain lake elevation. However, the apparently very high enthalpies of the concentration gradients observed, including BDE-209, suggest that bacterial anaerobic debromination also plays a significant role in the resulting altitudinal distributions. This microbial mechanism explains the relative abundances of PBDEs and their within lake differences between rocky and sediment microbial biofilms, thereby showing that the altitudinal pattern observed is not purely due to water temperature control on bacterial activity but also to changes in the availability of anaerobic microenvironments which increase with increasing lake productivity at lower altitudes.     

Population characteristics of young African women influencing prenatal exposure to DDT (Manhiça, Mozambique)

The concentrations of dichlorodiphenyltrichloroethane (DDT) compounds in cord blood of 214 children born between 2003 and 2006 in Manhiça (Mozambique) have been determined. In this time interval, corresponding to the period before DDT reintroduction for indoor residual spraying, the observed values averaged 0.8 and 0.4 ng/ml for 4,4′-dichlorodiphenyldichloroethylene (4,4′-DDE) and 4,4′-DDT, respectively, and were similar to those found in western countries. However, the 4,4′-DDT/4,4′-DDE ratio was high indicating that the inputs of these compounds arriving to children in utero originated from recent uses of the insecticide. The strongest factor affecting DDT concentration was parity. A well-defined decreasing concentration trend was observed for the cord blood concentrations in the period of study. The trend was also observed for multiparae and primiparae mothers independently. Children from multiparae women showed much lower concentrations than primiparae women. Children from mothers with secondary school level exhibited lower concentrations of these pesticides than mothers with lower degree of education.